Communication relay method and device

ABSTRACT

The wireless communication system configured in this manner performs priority control of communication as follows: (a) A wireless relay station stores a priority table in which, from among the communications handled by the stream server, the identifiers of those communications that are relayed with higher priority are registered. (b) The wireless relay device relays communications specified by the communication identifiers registered in the priority table with higher priority than other communications. (c) The stream server receives communication start requests from any of the wireless terminals and sends to the wireless relay station communication identifiers specifying the communications that are about to be started, and requests registration in the priority table. (d) The wireless relay station registers the communication identifiers whose registration has been requested in the priority table, to an extent that a proportion S/U of a sum S of consumption bandwidths of the communications specified by communication identifiers registered in the priority table to the available bandwidth U of the wireless network does not exceed a predetermined upper limit. Thus, flexible priority control is performed, and the quality of prioritized communication can be ensured.

FIELD OF THE INVENTION

The present invention relates to communication schemes in which aplurality of users belonging to the same communication area share alimited communication bandwidth, as in a wireless LAN (local areanetwork). More specifically, the present invention relates to suchcommunication schemes, wherein degrees of priority are assigned to eachof the communications of the plurality of users, and the quality ofcommunications with a high degree of priority is ensured.

BACKGROUND ART

In wireless data communication systems, such as wireless LANs, the samedata reaches wireless terminals that are present within an areareceiving the radio waves from a wireless relay station. That is to say,communication data between the wireless relay station and a givenwireless terminal is simultaneously communicated to the other terminalsas well. Consequently, it is not possible that a plurality of wirelessterminals simultaneously perform communication completely independentlyfrom one another. Therefore, when one wireless terminal starts to send alarge amount of data, the other wireless terminals will be influenced bythis communication. For example, effects such as a slow-down of thecommunication speed or delays in the response may occur. In VoIP (voiceover IP) technology, which is used in IP (internet protocol) telephones,audio data is communicated at predetermined intervals between a wirelessrelay station and a wireless terminal. In this situation, when acommunication necessitating a lot of communication bandwidth is startedby another wireless terminal, the audio data being communicated mayarrive at a certain delay. As a result, the audio of the communicationpartner may be reproduced at a delay, or a cut-off noise or the like mayoccur when the reproduction of the audio data occurs too late. For thisreason, there is a need for assigning priorities to certaincommunications when a plurality of communications are carried out. Thefollowing is an explanation of methods for priority control that havebeen proposed up to now.

IEEE 802.11 is an international standard for wireless LANs. There areseveral standards, depending on differences in the radio bands and themodulation method used. For example, the standard for wireless LANs thatare presently in wide use is IEEE 802.11b, which allows communication ata maximum of 11 Mbps in the 2.4 GHz band. This wireless LAN standard hastwo communication modes.

One communication mode is a mode called DCF (distributed coordinationfunction). In this mode, when no communication is performed, a wirelessterminal that wants to send data can send the data. When a plurality ofwireless terminals attempt to send data simultaneously, there is thepossibility of conflict among these communications, so that in theperiod after the previous communication has finished and until the nextcommunication starts, the standard mandates that each wireless terminalperforms the sending of data after waiting for a random standby time(referred to as “backoff time” below). Therefore, when there are aplurality of wireless terminals, the wireless terminals are each givenan equal opportunity to transmit, and no priority is given to any of thewireless terminals.

Another communication mode is the mode referred to as PCF (pointcoordination function). In this mode, the wireless relay station canintentionally secure the communication bandwidth for certain wirelessterminals periodically. However, currently available wireless LANsystems do not support the PCF mode, and at present, priority control inwireless LANs is not performed by a standardized method.

Recently, EDCF (enhanced DCF), which is an expansion of DCF, has beenconsidered as a part of the 802.11e standard. Whereas DCF provides onlyone send queue, EDCF provides a maximum of eight send queues. It hasbeen proposed to differentiate these send queues in accordance with thepriority degree of the communication data. With such a scheme, when senddata is stored in send queues with different degrees of priority, thenthe backoff times are set shorter for queues with higher degrees ofpriority. Therefore, data with a high degree of priority is more likelyto be sent.

Another proposal has been to prioritize certain communications byintentionally shortening the time that has to be waited after othercommunication has finished, when communicating in the DCF mode. Thiscommunication scheme operates without waiting for the backoff time thatis stipulated in the aforementioned 802.11 standard, but compatibilityis preserved, because it operates without problems even when operatingsimultaneously with devices conforming to the 802.11 standard. However,as the number of wireless terminals operating in this manner isincreased, there is the danger that the probability for contentionrises, and the communication quality decreases. Consequently, thisscheme is useful only when the number of prioritized communicationterminals is small.

The above-described prioritization methods are all methods performingthe priority control separately for each wireless terminal, that is,separately for each communication. By contrast, the following methods,for example, are methods in which the priority control is performeddepending on the data type to be communicated:

-   -   (a) Method using the value set for the layer-2 service class        (COS) in the user priority bits stipulated under 802.1Q;    -   (b) Method using IP priority order/DSCP (differential service        code bit) in the type-of-service (TOS) byte of the IPv4 header.

Both COS and TOS consist of three bits. It is possible to prioritize thepackets of a specific data type by determining a common packet priorityorder and referencing this information with the wireless terminals orthe data relay device. At present, as IP telephone equipment isdeveloped, this approach is adopted most often. However, in generalthere are only few devices that utilize this information, and there isthe risk that difficulties arise when mixing different services. Thereis furthermore the possibility that the entire network is put at riskwhen there are terminals with which an application operating on wirelessterminals and wired terminals is intentionally set to incorrect settingsin order to ensure a high priority degree.

Furthermore, JP 2003-134077A describes a method for sending videos withMPEG video encoding, in which an MPEG header is referenced and data isdistributed over a plurality of queues with different priority degrees.However, the algorithm for referencing the header and distribution tothe queues is fixed, so that it is difficult to dynamically change themethod of the priority control.

As described above, several methods for performing priority control on awireless LAN have been proposed. However, ordinarily the communicationbandwidth of wireless LANs is narrower than that of wired networks. Forthis reason, even when priority control is performed, it is conceivablethat most of the available bandwidth of the wireless network is used upby prioritized communication. In this case, there is the possibilitythat it is not possible to preserve the communication quality ofprioritized communication, even when performing priority control, due tothe influence that prioritized communications have on one another on acrowded network.

In order to perform stream communication as in VoIP over a wireless LAN,periodic communication must be realized reliably. There are thefollowing four problems regarding this:

-   -   (1) Priority control in wireless communication zones;    -   (2) Distribution of prioritized packets at wireless terminals        and relay device;    -   (3) Optimization of the method for determining which        communication should be prioritized;    -   (4) Bandwidth management of prioritized communication at the        wireless relay station.

Of these problems, problem (1) is realized by the above-describedmethods. Regarding the problems (2) and (3), it is desirable that it ispossible to switch flexibly, in accordance with the actual needs, forexample between priority control at the wireless terminal level,priority control at the application level or priority control accordingto data type. For example, it is preferable to give priority to IPtelephony over internet radio audio streams, even though both arestreamed audio. Moreover, it is desirable to enable settings that givepriority to IP phone calls by customers who pay for charge over IP phonecalls by customers who don't pay.

As for problem (4), there is a limitation on the bandwidth that can beused by wireless terminals performing prioritized communication, so thatone problem that arises is how conflicts among prioritizedcommunications can be solved. Moreover, in wireless LANs, when the stateof the wireless communication between the wireless terminals and thewireless relay station becomes poor and errors become frequent, then afunction is activated that reduces the connection speed to maintain thecommunication quality. When the connection speed is lowered and thetransferred data amount per unit time is kept the same, then theconsumption bandwidth is effectively broadened. Thus, it becomesnecessary to monitor the connection speed in the bandwidth management.

Furthermore, when there are a plurality of wireless relay stations, itmay occur that a wireless terminal is switched automatically, as aresult of being moved, from a wireless relay station to which it wasconnected previously to another nearby wireless relay station. In thiscase, it is expected that the prioritized communication that was alreadyrealized continues seamlessly even after the switch to another relaystation. Therefore, it is necessary to reserve a certain communicationbandwidth at the wireless relay station to which a wireless terminal ismoved from another wireless relay station. All of the above problemsneed to be considered for the bandwidth management of prioritizedcommunications.

It is an object of the present invention to realize stable wirelesscommunication by priority control of the communication of wirelessterminals.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, a communicationrelay method executed by a wireless communication system comprising aplurality of wireless terminals, a relay device connected by a wirelessnetwork to the wireless terminals, and a communication managing deviceconnected to the relay device by a wired network, comprises steps of:

-   -   storing, in the relay device, a priority table in which        identifiers of communications relayed with higher priority are        registered;    -   relaying, by the relay device, communication specified by the        communication identifiers stored in the priority table with        higher priority than other communication;    -   receiving, by the communication managing device, communication        start requests from any of the wireless terminals and sending        communication identifiers specifying the communications that are        about to be started to the relay device;    -   receiving, by the relay device, the communication identifiers        and registering the received communication identifiers in the        priority table, to an extent that a proportion S/U of a sum S of        consumption bandwidths of the communications specified by the        communication identifiers registered in the priority table to        the available bandwidth U of the wireless network does not        exceed a predetermined upper limit.

Using this communication relay method, communications that areregistered in the priority table are relayed with higher priority. Whichcommunications are handled with higher priority depends on whichcommunications are registered in the priority table. The registration ofcommunications in the priority table is performed in accordance with arequest of the communication managing device. Let us consider, forexample, the case that the communication managing device is a SIP servermanaging VoIP telephone communication. In this case, of all thecommunications performed by the wireless terminal, only VoIPcommunications are registered by the SIP server in the priority table.As a result, when the wireless terminal is performing a plurality ofcommunications, only the VoIP communications among those are relayedwith higher priority. That is to say, the priority control of whichcommunications are prioritized is not carried out within the wirelesssystem including the relay device and the wireless terminals, butsubstantially by a communication managing device that is arrangedoutside. Thus, there is the advantage that the method of the prioritycontrol can be flexibly changed, in accordance with the circumstances.

It should be noted that when the priority table is full, then the dataof VoIP communications that could not be registered may be subjected tosuch processing as not being relayed at all or being relayed withoutpriority. Data for communication other than VoIP communication is notmanaged by the SIP server, so that it cannot be registered in thepriority table and consequently is not relayed with higher priority.

According to a second aspect of the present invention, in thecommunication relay method according to the first aspect, the relaydevice registers communication identifiers in the priority table to anextent that the number of communications specified by the communicationidentifiers registered in the priority table is not greater than apredetermined number of connections.

Let us consider, for example, the case that VoIP communication isrelayed with higher priority in a wireless communication system inaccordance with IEEE 802.11b. The available bandwidth of the wirelessnetwork shared by the wireless terminals is 11 Mbps. Of this bandwidth,let 6.5 Mbps be reserved as the communication bandwidth for VoIPcommunication, and let the transfer data amount per unit of time forVoIP communication be 128 kbps. Thus, the maximum connection number thatcan be allowed for prioritized communication becomes 50. Consequently,50 communications can be registered in the priority table.

According to a third aspect of the present invention, in thecommunication relay method according to the first aspect, the relaydevice registers communication identifiers in the priority table to anextent that the sum of the consumption bandwidths of the communicationsspecified by the communication identifiers registered in the prioritytable is not greater than an available bandwidth of the wirelessnetwork.

Let us consider, for example, the case that VoIP communication isrelayed with higher priority in a wireless communication system inaccordance with IEEE 802.11b. The available bandwidth of the wirelessnetwork shared by the wireless terminals is 11 Mbps. Of this bandwidth,6.5 Mbps are reserved as the communication bandwidth for VoIPcommunication, and the consumption bandwidth of each of the wirelessterminals is registered in the priority table. The relay device controlsthe registration in the priority table such that the sum of theconsumption bandwidths of the wireless terminals does not exceed 6.5Mbps.

According to a fourth aspect of the present invention, in thecommunication relay method according to the first aspect, the relaydevice reserves, in the priority table, entries for guests in order totake over a relay of prioritized communication data that has beenrelayed by another relay device.

Wireless communication systems ordinarily include a plurality of relaydevices. Thus, it occurs that the relay device to which a wirelessterminal is wirelessly connected changes due to the movement of thewireless terminal. Accordingly, the relay devices reserve a provisionalcommunication bandwidth as resources for guests. Thus, even when thepriority communication bandwidth for existing terminals in the prioritytable of a given relay device is fully utilized, the communication ofthe wireless terminals that have moved to that relay device can berelayed seamlessly with higher priority.

According to a fifth aspect of the present invention, in thecommunication relay method according to the fourth aspect, the relaydevice exchanges with another relay device communication identifiersspecifying communication data relayed with higher priority, and updatesthe priority table based on a result of this exchange.

As the wireless terminal moves, the communication identifier listed inthe priority table of the relay device of the original location is sentto the priority table of the relay device of the destination location. Anew communication identifier is registered in the guest entries of thepriority table of the destination location, and the communicationidentifier is deleted from the entries for existing terminals in thepriority table of the original location. The priority tables are updatedas the wireless terminal moves, so that the bandwidth for prioritizedcommunication in the relay devices can be used advantageously.

According to a sixth aspect of the present invention, a communicationrelay system comprises:

-   -   a relay device connected by a wireless network to a plurality of        wireless terminals; and    -   a communication managing device connected by a wired network to        the relay device;    -   wherein the relay device comprises:        -   a priority table storing, from among a plurality of            communications by wireless terminals, identifiers of those            communications that are relayed with higher priority;        -   a relay means for relaying communication specified by the            communication identifiers stored in the priority table with            higher priority than other communication; and        -   a table managing means for receiving communication            identifiers from the communication managing device, and            registering received communication identifiers in the            priority table, to an extent that a proportion S/U of a sum            S of consumption bandwidths of the communications specified            by the communication identifiers registered in the priority            table to the available bandwidth U of the wireless network            does not exceed a predetermined upper limit;    -   wherein the communication managing device receives communication        start requests from any of the wireless terminals and sends to        the relay device communication identifiers specifying the        communication that are about to be started.

This system executes the communication relay method according to thefirst aspect of the present invention.

According to a seventh aspect of the present invention, a communicationmanaging device connected by a wired network to a relay device that isconnected by a wireless network to a plurality of wireless terminals,the communication managing device comprising:

-   -   a requesting means for receiving communication start requests        from any of the wireless terminals and sending to the relay        device an identifier of the communications that are about to be        started and requests for prioritized relay of these        communications;    -   a receiving means for receiving from the relay device responses        to these requests; and    -   a notification means for sending notifications to the wireless        terminals depending on the content of the response.

This device functions as a communication managing device in the wirelesssystem according to the first aspect of the present invention.

According to an eighth aspect of the present invention, a relay deviceconnected by a wireless network to a plurality of wireless terminals,comprises:

-   -   a connection means for connecting via a wired network to a        communication managing device managing communication of the        wireless terminals;    -   a storage means for storing a priority table in which        identifiers of communications relayed with higher priority are        registered;    -   a priority relay means for relaying communication data specified        by the communication identifiers stored in the priority table        with higher priority than other communication;    -   a request receiving means for receiving from the communication        managing device requests to register a communication identifier        in the priority table; and    -   a priority table updating means for registering the received        communication identifiers in the priority table, to an extent        that a proportion S/U of a sum S of consumption bandwidths of        the communications specified by the communication identifiers        registered in the priority table to the available bandwidth U of        the wireless network does not exceed a predetermined upper        limit.

This device functions as a relay device in the wireless system accordingto the first aspect of the present invention.

In accordance with the present invention, which communications areprioritized can be changed flexibly according to needs. Moreover, itpossible to prevent a deterioration of the quality of prioritizedcommunication due to conflicts among prioritized communications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the overall configuration of a wirelesscommunication system according to a first embodiment.

FIG. 2 is a functional diagram of the case that the wirelesscommunication system shown in FIG. 1 is applied to a wireless LAN.

FIG. 3 is a schematic illustration of the priority table shown in FIG.2.

FIG. 4 is a diagram showing the process flow that is performed by thewireless LAN system shown in FIG. 2.

FIG. 5 shows the functional configuration of a wireless LAN systemaccording to a second embodiment.

FIG. 6 is a schematic illustration of the signal administration tableshown in FIG. 5.

FIG. 7 is a schematic diagram of the priority table shown in FIG. 5.

FIG. 8 shows an administration table in which the priority table and thesignal administration table of a second embodiment have been combined.

FIG. 9 is an overall structural diagram of a wireless communicationsystem according to a fourth embodiment.

FIG. 10 is a functional diagram for the case that the wirelesscommunication system shown in FIG. 9 is applied to a wireless LAN.

FIG. 11 is a schematic diagram illustrating the priority table shown inFIG. 9.

FIG. 12 is a schematic diagram illustrating the connectionadministration table shown in FIG. 9.

FIG. 13 is a diagram showing the process flow in the wireless LAN systemshown in FIG. 10.

FIG. 14 is a diagram showing the process flow in the wireless LAN systemaccording to a fifth embodiment.

FIG. 15 is a diagram showing the process flow in the wireless LAN systemaccording to another embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Overview of the Invention

According to an embodiment of the present invention, in an ordinarywireless communication system, such as a wireless LAN or the like,priority control is substantially carried out not within the system butoutside of the system. Ordinary wireless communication systems include aplurality of wireless terminals and a wireless relay station(corresponding to a “relay device”) connected through a wireless networkto the wireless terminals. In an embodiment of the present invention, astream server (corresponding to a “communication managing device”)managing the communication performed by the wireless terminals isfurther added to the wireless communication system. A wirelesscommunication system configured like this performs priority control ofcommunication in the following manner:

-   -   (a) The wireless relay station stores, from among the        communications managed by the stream server, the identifiers of        those communications that are relayed with higher priority in a        priority table.    -   (b) The wireless relay station relays the communications        specified by the communication identifiers registered in the        priority table with higher priority than other communications.    -   (c) The stream server receives a communication start request        from any of the wireless terminals, and sends a communication        identifier specifying the communication to be started to the        wireless relay station, requesting registration in the priority        table.    -   (d) The wireless relay station registers the communication        identifier for which registration is requested in the priority        table, to an extent that a proportion S/U of a sum S of a        consumption bandwidth of communication specified by        communication identifiers registered in the priority table to        the available bandwidth U of the wireless network does not        exceed a predetermined upper limit.

Using this communication relay method, the communications registered inthe priority table are relayed with higher priority. Communicationsrelayed with higher priority are also referred to as “prioritizedcommunications” in the following. An upper limit is set in advance forthe bandwidth, within the available bandwidth of the wireless network,that is assigned for prioritized communications (also referred to as“resources for prioritized communication” in the following). Whichcommunications are prioritized communications is determined according towhich communications are registered in the priority table. Theregistration of communications in the priority table is performed inaccordance with requests by the stream server. The stream server managesthe communication of the wireless terminals, and may request that allthese communications are handled as prioritized communications.Conversely, the stream sever may also request from the wireless relaystation that only a portion of the communications handled by the streamserver are handled as prioritized communications.

That is to say, which communications are prioritized is not decided inadvance within an ordinary wireless system including a wireless relaystation and wireless terminals, but is substantially determined by astream server outside the system. Therefore, there is the advantage thatwireless terminals and applications eligible for prioritizedcommunication can be flexibly set in accordance with various externalconditions. Moreover, the registrations of prioritized communications inthe priority table are restricted such that the upper limit forresources for prioritized communication is not exceeded, so that thequality of prioritized can be ensured.

It should be noted that there are cases in which no resources forprioritized communication are available, regardless of whether thestream server has requested registration or not. Thus, when the prioritytable is full, then the communications that could not be registered maybe subjected to such processing as not being relayed at all by thewireless relay station or being relayed without priority. For example,if the application is an IP telephone and a call from a wirelessterminal is not relayed by the wireless relay station, then the user maybe notified that the called IP phone is busy or out of range. Since thestream server is not concerned with communications that are not handledby the stream server, they cannot be registered in the priority table.Consequently, they are not relayed with higher priority.

First Embodiment

(1) Configuration

FIG. 1 shows the overall configuration of a wireless communicationsystem according to a first embodiment. The wireless communicationsystem includes at least one wireless relay station 1 a, 1 b, a streamserver 2, and a plurality of wireless terminals 3 a to 3 d. Thefunctional configurations of the wireless relay stations and thewireless terminals are the same, and unless it is necessary todifferentiate between them, they are referred to without the letters a,b, etc.

The wireless terminals 3 can be connected via a wireless LAN to any ofthe wireless relay stations 1. The wireless stations 1 are connected toone another by a wired LAN 4 (see FIG. 2). Furthermore, the wirelessrelay stations 1 are connected via a wired LAN 4 to a stream server 2.

The stream server 2 handles all or a portion of the wirelesscommunication of the wireless terminals 3, and uses communicationidentifiers to discriminate the various communications to be handled. Anexample of the stream server 2 and the communication handled by thestream server 2 is communication handled by an SIP server. Anotherexample is communication handled by an authentication server. However,the stream server 2 is not limited to these examples.

FIG. 2 is a functional diagram of the case that the wirelesscommunication system shown in FIG. 1 is applied to a wireless LAN. Inthe following, to keep explanations simple, an example is explained inwhich an SIP server 2 is used as the stream server, and VoIPcommunication is relayed with higher priority.

Wireless Relay Station

The following is a description of the elements of the wireless relaystations 1. The function of the elements of each of the wireless relaystations 1 is the same, so that unless it is necessary to differentiatebetween them, they are referred to without the letters a, b, etc.

-   -   (a) Bandwidth managing portion 11: The bandwidth managing        portion 11 manages a priority table 111. In the priority table        111, communication identifiers for identifying prioritized        communications are registered. The bandwidth managing portion 11        updates the priority table 111 in response to messages from the        SIP server 2. A more detailed explanation of the priority table        111 is given further below.    -   (b) Priority order managing portion 12: The priority order        managing portion 12 manages the priority order of the        prioritized communications registered in the priority table 111.        More specifically, the priority order managing portion 12        ordinarily determines the priority order in the order of        arrival, and when a plurality of prioritized communications        occur at the same time, it also determines which is to be given        priority. However, if a PCF or other relay station performing        central control of the communication of the wireless terminals        is arranged between the wireless terminals 3 and the wireless        relay station 1, then it is necessary to manage the priority        order of the wireless terminals 3. If there are no particular        problems, it is possible to set the priority order to the order        in which entries are made in the priority table.    -   (c) Priority order instruction portion 13: The priority order        instruction portion 13 gives instructions to the wireless LAN        interface 15, such that the prioritized communications are        processed in accordance with the priority order.    -   (d) Priority communication discrimination portion 14: The        priority communication discrimination portion 14 discriminates        whether communication data received through a wired LAN        interface 16 (explained below) is data for a prioritized        communication or not. This judgment is made by looking up        whether the communication identifier of the received data is        stored in the priority table 111 or not.    -   (e) Wireless LAN interface 15: The wireless LAN interface 15        performs the access control in accordance with the standard for        wireless LANs. Moreover, the wireless LAN interface 15 relays        the communications registered in the priority table 111 with        higher priority than the non-prioritized communication in the        wireless zone, in accordance with the priority order specified        by the priority order instruction portion 13. For the method for        relaying with higher priority, any of the methods proposed in        the conventional art can be utilized. For example, it is        possible to use a priority communication scheme as discussed for        standardization in accordance with IEEE 802.11e.    -   (f) Wired LAN interface 16: The wired LAN interface 16 performs        the access control in accordance with the standard for wired        LANs.    -   (g) Stream Server communication portion 17: The stream server        communication portion 17 exchanges data with the SIP server 2        through the wired LAN interface 16.

FIG. 3 is a schematic illustration of the priority table 111. Thepriority table 111 registers communication identifiers and communicationstates of prioritized communications. The IP addresses and port numbersof the sender and the receiver are used as the communicationidentifiers. Whether a communication identifier is registered in thepriority table 111 is decided by whether the following expression issatisfied:S/U≦(predetermined upper limit)where S: sum of the consumption bandwidth of communications registeredin the priority table 111;

-   -   U: available bandwidth U of the wireless LAN shared by the        plurality of wireless terminals 3.

The available bandwidth of the wireless LAN that is determined by thisupper limit constitutes the resources for prioritized communication. Inthis example, the number of entries in the priority table 111 aredetermined, and if there are empty entries, it is judged that resourcesfor prioritized communication are available. The number of entries canbe decided as described below.

For example, let us consider the case that VoIP communication is relayedwith higher priority in a wireless LAN system in accordance with IEEE802.11b. The available bandwidth of the wireless LAN shared by thewireless terminals 3 is 11 Mbps. Of this bandwidth, 6.5 Mbps arereserved as the communication bandwidth for VoIP communication, that is,as the resources for prioritized communication. The transfer data amountper unit of time for VoIP communication with the wireless terminals 3 isassumed to be 64 kbps×2=128 kbps, in consideration of two-way sendingand receiving. Thus, the maximum connection number that can be allowedfor prioritized communication is given by 6.5M/128 k, and is thus 50.Consequently, 50 entries should be generated in the priority table 111.Thus, a maximum of 50 prioritized communications can be registered inthe priority table 111.

SIP Server

The SIP server 2 has the following elements:

-   -   (a) Connection terminal managing portion 21: The connection        terminal managing portion 21 stores the communication        identifiers identifying the communications handled by the SIP        server 2. Examples of communication identifiers are the IP        addresses and port numbers of the sender and the receiver of a        data stream.    -   (b) SIP protocol control portion 22: The SIP protocol control        portion 22 controls the communication data that is exchanged        with the wireless LAN interface 24, which is VoIP communication        data in this example, based on the SIP protocol.    -   (c) External link portion 23: The external link portion 23        requests prioritized communication from the wireless relay        station 1.    -   (d) Wired LAN interface 24: The wired LAN interface 24 performs        access control in accordance with the standard for wired LANs.        Wireless Terminals

The following is a description of the elements of the wireless terminals3. The function of the elements of each of the wireless relay stations 1is the same, so that unless it is necessary to differentiate betweenthem, they are referred to without the letters a, b, etc.

-   -   (a) IP telephone application 31: The IP telephone application 31        performs access control in accordance with the standard for VoIP        telephony.    -   (b) Priority communication discrimination portion 32: The        priority communication discrimination portion 32 discriminates        which of the communications carried out by the wireless        terminals 3 are prioritized communications. This judgment can be        performed as follows. For VoIP communication carried out by        wireless terminals, the IP address and (if necessary) the port        number of the other communication party are stored (not shown in        the drawings). When the VoIP communication starts, a message        indicating whether the beginning communication is a prioritized        communication is received from the SIP server 2 and stored (not        shown in the drawings). Based on the stored information, the        send data are passed on to the priority communication        instruction portion 33 while differentiating the send data        according to prioritized communication and non-prioritized        communication.    -   (c) Priority communication instruction portion 33: The priority        communication instruction portion 33 passes the send data on to        the wireless LAN interface 34. When doing so, the priority        communication instruction portion 33 indicates whether the data        are for prioritized communication or non-prioritized        communication.    -   (d) Wireless LAN interface 34: The wireless LAN interface 34        performs access control in accordance with the standard for        wireless LANs.        (2) Process Flow

FIG. 4 is a diagram showing the process flow that is performed by thewireless LAN system shown in FIG. 2. In order to facilitateexplanations, an example is given in which the plurality of wirelessterminals 3 a and 3 b can be both connected to any same wireless relaystation 1 a.

When the wireless terminal 3 a is started up, the wireless LAN interface34 a sends a message searching for a wireless relay station 1. Thewireless relay station 1 a, which is capable of wireless connection,responds to this. The wireless terminal 3 a connects to the wirelessrelay station 1 a that has responded (#1).

After that, the IP telephone application 31 a of the wireless terminal 3a sends to the SIP server 2 a Register message with information aboutthe wireless terminal 3 a, such that the wireless terminal 3 a functionsas a VoIP terminal with respect to the SIP server 2 (#2). For example,the IP application 31 a of the wireless terminal 3 a sends to the SIPserver 2 the IP address and the port number of the wireless terminal 3a, and the identifier for calling up the wireless terminal 3 a(telephone number, user ID, SIP address or the like). In order to callup by IP telephone other terminals using this identifier, thisinformation is registered in the SIP server 2. The SIP server 2 notifiesthe actual IP address and port number based on the identifier of thewireless terminals 3, when performing an actual call process. If thisregistration is successful, the SIP server 2 sends an OK message to thewireless terminal 3 a (#3).

Similarly, the wireless terminal 3 b performs the wireless connection tothe wireless relay station 1 a (#4), and the identifier for calling upthe wireless terminal 3 b is registered in the SIP server 2 (#5, #6).

The following is an explanation of an example in which the wirelessterminal 3 a initiates a VoIP call to the wireless terminal 3 b, whilethe wireless terminals 3 a and 3 b are both IP-connected in this mannerto the wireless relay station 1 a.

The IP telephone application 31 a of the wireless terminal 3 a sends adialing message (Invite) to the SIP server 2. Since the prioritycommunication discrimination portion 32 a does not recognize thiscommunication to be a prioritized communication, it is judged to be anon-prioritized communication. The priority communication instructionportion 33 a instructs the wireless LAN interface 34 a to performnon-prioritized communication. The Invite message is transferred fromthe wireless LAN interface 15 of the wireless relay station 1 a to thewired LAN interface 16, and is sent via the wired LAN 4 to the SIPserver 2 (#7). The wired LAN interface 24 of the SIP server 2 receivesthe Invite message, and passes it on to the SIP protocol control portion22. The SIP protocol control portion 22 interprets it to mean that thereis a call from the wireless terminal 3 a to the wireless terminal 3 b.

Furthermore, the SIP server 2 queries the wireless relay station 1 awhether resources for prioritized communication are available. In otherwords, it queries whether the priority table 111 of the wireless relaystation 1 a has enough capacity for registering a total of fourcommunications, namely the respective communications between thewireless terminals 3 a and 3 b and the wireless relay station 1 a. Thetwo communication paths for sending and receiving that are necessary forone call can be registered in one entry, so that it is queried whethertwo entries are available to register four communication paths. Thisquery (referred to below as “bandwidth confirmation message”) is sent bythe external link portion 23 via the wired LAN interface 24 (#8). Thisbandwidth confirmation message includes an identifier of thecommunication selected by the SIP server 2 as prioritized communication.

The stream server communication portion 17 of the wireless relay station1 a extracts the bandwidth confirmation message and queries thebandwidth control portion 11 about the availability of resources forprioritized communication. The bandwidth control portion 11 refers tothe priority table 111, and if resources are available, writes thereceived communication identifier into the priority table 111.Furthermore, the bandwidth managing portion 11 sets the communicationstate to “not connected.” Then, the SIP server 2 is notified thatresources have been reserved, or that no resources were available. Thismessage is sent from the stream server communication portion 17 to theexternal link portion 23 of the SIP server 2 (#9).

When the external link portion 23 of the SIP server 2 is notified thatresources have been reserved, then this is notified to the SIP protocolcontrol portion 22. Receiving this notification, the SIP protocolcontrol portion 22 sends a connection request (Invite) to the wirelessterminal 3 b (#10). At the same time, the SIP protocol control portion22 sends a Trying message to the wireless terminal 3 a (#11). On theother hand, the SIP server 2 may also send an Invite message to thewireless terminal 3 b even if resources for prioritized communicationare not available. In this case, all or some of the communicationbetween the wireless terminals 3 a and 3 b in the wireless zone istreated as non-prioritized communication. On the other hand, if it isnot possible to handle all of the communication between the wirelessterminals 3 a and 3 b in the wireless zone as prioritized communication,the SIP server 2 may also send a disconnection message to the wirelessterminal 3 a without establishing a connection between the wirelessterminals 3 a and 3 b.

If resources for prioritized communication between the wirelessterminals 3 a and 3 b are available, the wireless terminal 3 b firstsends a Ringing message to the SIP server 2. The Ringing message isrelayed to the wireless terminal 3 a (#13). Even though the Invite andthe Ringing messages pass through the wireless relay station 1 a, thecommunication between the SIP server 2 and the wireless terminals 3 aand 3 b is not prioritized communication. Therefore, the two messagesare judged to be non-prioritized communication by the prioritycommunication discrimination portion 14 of the wireless relay station 1a. The priority order instruction portion 13 sends the respectivemessages as non-prioritized communication to the wireless terminals 3 aand 3 b via the wireless LAN interface 15 (#10 to #13). It should benoted that in order to turn the communication between the SIP server 2and the wireless relay station la into prioritized communication, it ispossible to assign resources for prioritized communication to thiscommunication. This method is explained below in the second embodiment.

When the user of the wireless terminal 3 b responds to the Invitemessage, then an OK message is sent from the IP telephone application 31b of the wireless terminal 3 b via the wireless relay station 1 a to theSIP server 2 (#14).

At the SIP server 2, this response message is interpreted by the SIPprotocol control portion 22. Based on the interpretation, the SIPprotocol control portion 22 notifies the wireless relay station 1 a viathe external link portion 23 of the establishment of the connection.Obtaining this notification, the bandwidth control portion 11 changesthe communication state of the corresponding entry in the priority table111 to “communicating.” Thus, all or a portion of the VoIP communicationbetween the wireless terminals 3 a and 3 b becomes prioritizedcommunication in the wireless zone (#15).

The SIP protocol control portion 22 sends a response message (OK) viathe wired LAN interface 24 and through the wireless relay station 1 a tothe wireless terminal 3 a (#16). The response message includes a messageindicating whether the two (i.e. upstream and downstream) communicationsbetween the wireless terminal 3 a and the wireless relay station la are,respectively, prioritized communications or not. The wirelesscommunication discrimination portion 32 a of the wireless terminal 3 astores the received response message. The wireless terminal 3 areceiving this response message sends a response message (ACK) via theSIP server 2 to the wireless terminal 3 b (#17, #18).

After this, the call between the wireless terminals 3 a and 3 b begins.The communicated VoIP packets are judged to be prioritized communicationby the priority communication discrimination portions 32 a and 32 b ofthe wireless terminals 3 a and 3 b, and by the priority communicationdiscrimination portion 14 of the wireless relay station 1 a. Thus, thewireless LAN interfaces of the wireless terminals 3 a, 3 b and thewireless relay station 1 a are instructed to perform prioritizedcommunication.

In order to interrupt the VoIP communication, an interrupt message (Bye)is sent from one of the wireless terminals. In this example, a Byemessage is sent from the wireless terminal 3 a. When the IP telephoneapplication 31 a sends a Bye message, it is sent via the wireless relaystation 1 a to the SIP server 2 (#19).

The SIP protocol control portion 21 sends the Bye message via thewireless relay station 1 a to the wireless terminal 3 b on the otherside (#20).

The IP telephone application 31 b confirms the Bye message and respondsvia the wireless relay station 1 b, whereupon the SIP protocol controlportion 22 interprets this response (#201).

The SIP protocol control portion 22 notifies the termination of theprioritized communication via the external link portion 23 to the streamserver communication portion 17 of the wireless relay station 1 a.Receiving this notification, the bandwidth managing portion 11 of thewireless relay station 1 a eliminates the entry for the correspondingprioritized communication from the priority table 111 (#202).

The SIP protocol control portion 22 further sends a response message viathe wireless relay station 1 a to the wireless terminal 3 a, andterminates all communication with regard to the VoIP communication(#203).

With the above-described process, a prioritized communication isregistered in the priority table 111 in response to a request from theSIP server 2. Consequently, if there is a change in which communicationis prioritized, that is, if the method of the priority control ischanged, then the algorithm of the SIP server 2 should be changed. Thatis to say, by integrating the priority table 111 in the wireless relaystation of an existing wireless communication system and adding a streamserver 2, such as a SIP server, it is possible to change the method ofthe priority control easily and flexibly. In this example, only VoIP isprioritized, so that IP data from the same wireless terminal 3 that isnot data for VoIP communication is not prioritized. In other words, itis possible to relay only the communication with regard to specifiedapplications, such as IP telephone applications for example, with higherpriority. Moreover, since registration in the priority table isperformed to an extent that does not exceed the resources forprioritized communication, it can be prevented that there is contentionamong prioritized communications, leading to a deterioration ofcommunication quality.

Second Embodiment

In the first embodiment, an upper limit is provided for the number ofprioritized communications registered in the priority table 111, thusrestricting the registrations in the priority table 111. Another methodis to judge whether resources for prioritized communication areavailable based on the bandwidth that the wireless terminals 3 consumeby wireless communication (referred to as “consumption bandwidth” in thefollowing).

FIG. 5 shows the functional configuration of a wireless relay station 1,a SIP server 2 and wireless terminals 3 according to a secondembodiment. Elements having the same function as in the first embodimentare denoted by the same reference numerals. Differences to the firstembodiment are the fact that a signal administration table 112 isprovided, as well as the information stored in the priority table 113.

FIG. 6 is a schematic illustration of the signal administration table112. Registered in the signal administration table 112 are communicationidentifiers identifying the communication data communicated from the SIPserver 2 to any of the communication terminals and the communicationdata communicated from any of the communication terminals to the SIPserver 2. FIG. 6 shows the case that the IP address of the SIP server 2is “192.168.1.5” and the port number of the SIP server 2 is “5060.” Theasterisk “*” in FIG. 6 represents an arbitrary sender or an arbitraryrecipient. By providing the signal administration table 112 to assignresources for prioritized communication to the communication between theSIP server 2 and the wireless relay station 1, it is possible to let thewireless relay station 1 send IP communication control message exchangedbetween the SIP server 2 and the wireless relay station 1 with higherpriority. Consequently, seen from the user of the wireless terminal 3,there is the effect that the standby time for calling another terminalis shortened, even when the wireless network is congested. The signaladministration table 112 is managed and updated by the bandwidthmanaging portion 11 of the wireless terminal 3.

FIG. 7 is a schematic diagram of the priority table 113. In thispriority table 113, communication identifiers, consumption bandwidthsand communication states of prioritized communications are registered.The IP address and port number of the sender and the receiver are usedfor the communication identifiers. Whether a communication identifier isregistered in the priority table 113 depends on whether the sum of theconsumption bandwidth of the prioritized communications registered inthe priority table 113 becomes lower than the resources for prioritizedcommunication. “Consumption bandwidth” means the communication bandwidthused by the wireless terminals 3. It should be noted, however, that inwireless LANs the communication speed between the wireless terminal 3and the wireless relay station 1 changes depending on the communicationstate, so that it is necessary to use a converted value, unlesscommunication is performed at the maximum communication speed. Let usconsider for example the case that the maximum communication speed is 11Mbps, and a given wireless terminal 3 communicates for some reason at5.5 Mbps. This communication at 5.5 Mbps necessitates twice thecommunication time for communication of the same amount of data thancommunication at 11 Mbps. This means that by communicating at 5.5 Mbps,twice the consumption bandwidth of communication at 11 Mbps is used. Forexample, if VoIP communication is carried out by G.711, then theconsumption bandwidth at 11 Mbps is 128 kbps, but at 5.5 Mbps, it ismanaged as a consumption bandwidth of 256 kbps. The calculation of theconsumption bandwidth is performed by the bandwidth managing portion 11of the wireless relay station 1.

Whether a communication is registered in the priority table 113 isdecided for example as follows. Let us consider the case that VoIPcommunication is relayed with higher priority in a wirelesscommunication system in accordance with IEEE 802.11b. Let the availablebandwidth of the wireless LAN shared by the wireless terminals 3 be 11Mbps. Of those 11 Mbps, 6.5 Mbps are reserved as the communicationbandwidth for VoIP communication, that is, as the resources forprioritized communication. The consumption bandwidth of the wirelessterminals is converted, taking as a reference the case that the transferdata amount per unit time of the wireless terminals 3 is 11 Mbps, andwritten into the priority table 113. Then, new prioritizedcommunications are registered in the priority table 113 to an extentthat the sum of the consumption bandwidth of the wireless terminals 3does not exceed 6.5 Mbps.

Except for the method of judging whether a communication is registeredin the priority table 113 and the aspect that the signal administrationtable 112 is used, the wireless LAN system of this embodiment performsthe same process as in the first embodiment. Consequently, if sufficientresources for prioritized communication are provided, then it ispossible to control which communication the external SIP server 2handles with priority, and to avoid contention among prioritizedcommunications.

Third Embodiment

In the first and the second embodiment, it is possible to combine thepriority table 111 or the priority table 113 and the signaladministration table 112 to one table.

FIG. 8 shows an administration table in which the priority table 113 andthe signal administration table 112 of the second embodiment have beencombined. It is possible to perform the same processing as describedabove, when using the administration table shown in FIG. 8 instead ofthe priority table 111 shown in FIG. 1, or instead of the combination ofthe priority table 113 and the signal administration table 112 shown inFIG. 6. The communication bandwidth necessary for the signalingcommunication can be calculated based on the number of wirelessterminals or the connection process frequency.

Fourth Embodiment

(1) Configuration

The wireless relay station 1 to which a wireless terminal 3 is connectedmay change as the wireless terminals 3 moves. It is preferable that theprioritized communication performed with a given wireless relay station1 a can be continued seamlessly also with the wireless relay station 1 bto which the wireless terminal 3 is moved. For this reason, theresources for prioritized communication may be divided into resourcesfor existing parties and guest resources for moving parties. Byreserving guest resources, it is possible to reserve resources forprioritized communication with wireless terminals 3 that are connectedby moving.

FIG. 9 is an overall structural diagram of a wireless communicationsystem according to a fourth embodiment. Elements having the samefunction as in the first to third embodiments are denoted by the samereference numerals. In this embodiment, the wireless communicationsystem includes a plurality of wireless relay stations, and furthermorean access point manager 5 (referred to as “AP manager” below). In orderto simplify the explanations, the following is an example in which awireless terminal 3 a is moved from a region administrated by a wirelessrelay station 1 a (see FIG. 9A) to a region administrated by a wirelessrelay station 1 b (see FIG. 9B).

FIG. 10 is a functional diagram of each of the elements for the casethat the wireless communication system shown in FIG. 9 is applied to awireless LAN. In FIG. 10, the same functions as in Embodiment 1 to 3 aredenoted by identical reference numerals. The wireless relay station 1 bhas the same functional configuration as the wireless relay station 1 a.As above, an example is explained in which an SIP server 2 handling VoIPcommunication is used as the stream server 2, and VoIP communication isrelayed with higher priority.

The AP manager 5 has the following structural elements.

-   -   (a) Access point managing portion 51: The access point managing        portion 51 has a connection administration table 511, and        manages the relation between the wireless terminals 3 and the        wireless relay stations 1 based on this connection        administration table 511.    -   (b) Stream server control relay portion 52: The stream server        control relay portion 52 exchanges data with the SIP server 2.    -   (c) Wired LAN interface 53: The wired LAN interface 53 performs        access control in accordance with the standard for wireless        LANs.

FIG. 11 is a schematic diagram illustrating a priority table 114 havingentries for existing parties and entries for guests. The sum of entriesfor existing parties and entries for guests is controlled such that theupper limit for the maximum number of connections determined by themethod described in the first embodiment is not exceeded. The ratiobetween the two is adjusted as appropriate in accordance with thelocation at which the wireless relay stations 1 are set up. Moreover,the ratio between the two does not always have to be constant and mayalso be changed in accordance with the number of wireless terminals thatare used while moving. Prioritized communications of wireless terminals3 connected for at least a predetermined time T to the wireless relaystation 1 having this table are registered in the entries for theexisting parties. Prioritized communications of wireless terminals 3that have moved from a region administrated by another wireless relaystation 1 are registered in the entries for guests. The prioritizedcommunications registered in the entries for guests are moved to theentries for existing parties when a predetermined time T has passedafter their registration.

The communication identifier for the prioritized communication of aguest entry is sent from another wireless relay station 1. That is tosay, as the wireless terminal 3 moves, the communication identifierlisted in the priority table 114 a of the wireless relay station 1 a atthe original location is sent to the priority table 114 b of thewireless relay station 1 b at the destination location. Then, theprioritized communication performed by this wireless terminal 3 is newlyregistered in the guest entries of the priority table 114 b at thedestination location, and deleted from the entries for existingterminals of the priority table 114 a at the original location. As thewireless terminal 3 moves, the priority table 114 of the associatedwireless relay stations 1 is updated, so that the wireless terminal 3can seamlessly perform prioritized communication. Moreover, the wirelessrelay stations 1 can effectively use resources for prioritizedcommunication that have become unnecessary.

It should be noted that in this example, an upper limit is set for thenumber of entries, that is, the number of connections, restrictingregistrations in the priority table 114, but it is of course alsopossible to restrict registrations by monitoring the consumptionbandwidth, as described above (see second embodiment above). Moreover,it is also possible to further integrate the signal administration table112 into the priority table 114, as shown in the third embodiment.

FIG. 12 is a schematic diagram illustrating a connection administrationtable 511. This table oversees which wireless terminal 3 is connected towhich wireless relay station 1. More specifically, this table stores theIP addresses of the wireless terminals 3 and the IP addresses of thewireless relay stations 1 to which those wireless terminals 3 areconnected. Based on this, it is possible to query a wireless relaystation 1 to which the wireless terminals 3 are connected whetherresources for prioritized communication are available.

(2) Processing

FIG. 13 is a diagram showing the process flow in the wireless LAN systemshown in FIG. 10.

When the wireless terminal 3 a is started up, the wireless LAN interface34 a sends a message searching for a wireless relay station 1. Thewireless relay station 1 a, which is capable of connecting to thewireless terminal 3 a, responds to this. The wireless terminal 3 aconnects to the wireless relay station 1 a that has responded (#21).

The wireless relay station 1 a sends information about the wirelessterminal 3 a and the wireless relay station 1 a to the AP manager 5(#22). The stream server control relay portion 52 of the AP manager 5receives this information, and passes it on to the access point managingportion 51. Thus, the association of the wireless terminal 3 a and thewireless relay station 1 a is registered in the connectionadministration table 511. It should be noted that in this example, thereis no particular limitation to the timing at which the relation betweenthe wireless terminals 3 and the wireless relay stations is registered.For example, it is possible that the wireless relay station 1 registersthis information in the AP manager 5 at the stage when the wirelessterminal 3 is wirelessly connected, at the stage when the wirelessterminal 3 sends the Register message to the SIP server 2, or at thestage when the wireless terminal 3 sends the Invite message to the SIPserver 2.

After that, information of the wireless terminal 3 a is sent from thewireless terminal 3 a to the SIP server 2, such that that the wirelessterminal 3 a functions as a VoIP terminal with respect to the SIP server2 (#23). For example, the IP telephone application 31 a of the wirelessterminal 3 a registers the IP address and port number of the wirelessterminal 3 a, and an identifier (telephone number, user ID, SIP addressor the like) for calling up the wireless terminal 3 a. When thisregistration is successful, the SIP server 2 sends an OK message to thewireless terminal 3 a (#24).

The wireless terminal 3 b connects to the wireless relay station 1 b(#25), is registered in the AP manager 5 (#26) and registered in the SIPserver 2 (#27, #28) in the same manner as the wireless terminal 3 a.

The following is an explanation of an example in which the wirelessterminal 3 a initiates a VoIP call to the wireless terminal 3 b, whilethe wireless terminals 3 a and 3 b are both IP-connected in this mannerto the wireless relay station 1 a.

The IP telephone application 31 a of the wireless terminal 3 a sends anInvite message to the SIP server 2 (#29). Since the prioritycommunication discrimination portion 32 a does not recognize thiscommunication to be a prioritized communication, it is judged to be anon-prioritized communication. The priority communication instructionportion 33 a instructs the wireless LAN interface 34 a to performnon-prioritized communication. The Invite message is transferred fromthe wireless LAN interface 15 a of the wireless relay station la to thewired LAN interface 16 a, and is sent via the wired LAN 4 to the SIPserver 2. The wired LAN interface 24 of the SIP server 2 receives theInvite message, and passes it on to the SIP protocol control portion 22.The SIP protocol control portion 22 interprets it to mean that there isa call from the wireless terminal 3 a to the wireless terminal 3 b.

Furthermore, the SIP server 2 queries the AP manager 5 whether resourcesfor prioritized communication are available (#30).

The AP manager 5 looks up the communication administration table 511,and performs a bandwidth confirmation with the wireless relay station 1a connected to the wireless terminal 3 a (#31).

At the wireless relay station 1 a, the stream server communicationportion 17 a extracts the bandwidth confirmation message and queries thebandwidth control portion 11 a about the availability of resources forprioritized communication. The bandwidth control portion 11 a refers tothe priority table 114 a, and if resources are available, writes thereceived communication identifier into the priority table 114 a.Furthermore, the bandwidth managing portion 11 a sets the communicationstate to “not connected.” If there is bandwidth available at thewireless relay station 1 a, then an OK message is sent back from thestream server communication portion 17 a of the wireless relay station 1a to the AP manager 5 (#32). The AP manager 5 returns this OK message tothe external link portion 23 of the SIP server 2 (#33). The bandwidthconfirmation message includes an identifier of the communicationselected by the SIP server 2 as prioritized communication.

Similarly, the SIP server 2 queries the wireless relay station 1 b viathe AP manager 5 whether resources are available for the wirelesscommunication between the wireless terminal 3 b and the wireless relaystation 1 b, and receives the response to this (#34 to #37).

When notified that resources have been reserved, the external linkportion 23 of the SIP server 2 notifies this to the SIP protocol controlportion 22. Receiving this, the SIP protocol control portion 22 sends anInvite message to the wireless terminal 3 b (#38). Similarly, the SIPprotocol control portion 22 sends a Trying message to the wirelessterminal 3 a (#39). If there are no resources for prioritizedcommunication available in either one or both of the wireless relaystations 1 a and 1 b, then the SIP server 2 may also send an Invitemessage to the wireless terminal 3 b. In this case, all or some of thecommunication between the wireless terminals 3 a and 3 b in the wirelesszone is treated as non-prioritized communication. On the other hand, ifit is not possible to handle all of the communication between thewireless terminals 3 a and 3 b in the wireless zone as prioritizedcommunication, the SIP server 2 may also send a disconnection message tothe wireless terminal 3 a without establishing a connection between thewireless terminals 3 a and 3 b.

If a connection is established between the wireless terminals 3 a and 3b, the wireless terminal 3 b first sends a Ringing message to the SIPserver 2 (#40). The Ringing message is relayed to the wireless terminal3 a (#41). As mentioned above, it is preferable to assign resources forprioritized communication to the communication data exchanged by the SIPserver 2, such as Invite messages and Ringing messages.

When the user of the wireless terminal 3 b responds to the Invitemessage, then an OK message is sent from the IP telephone application 31b of the wireless terminal 3 b via the wireless relay station 1 a to theSIP server 2 (#42).

At the SIP server 2, this response message is interpreted by the SIPprotocol control portion 22. Based on the interpretation, the SIPprotocol control portion 22 notifies the wireless relay stations 1 a and1 b via the external link portion 23 that a connection has beenestablished (#43, #44). Receiving this notification, the bandwidthcontrol portions 11 a and 11 b change the communication state of thecorresponding entries in the priority tables 114 a and 114 b to“communicating.” Thus, all or a portion of the VoIP communicationbetween the wireless terminals 3 a and 3 b becomes prioritizedcommunication in the wireless zone.

The SIP protocol control portion 22 of the SIP server 2 further sends aresponse message (OK) via the wired LAN interface 24 and through thewireless relay station 1 a to the wireless terminal 3 a (#45). Theresponse message includes a message indicating whether the two (i.e.upstream and downstream) communications between the wireless terminal 3a and the wireless relay station 1 a are prioritized communications ornot.

The wireless terminal 3 a sends a response message (ACK) via the SIPserver 2 to the wireless terminal 3 b (#46, #47). The response messageincludes a message indicating whether the two (i.e. upstream anddownstream) communications between the wireless terminal 3 b and thewireless relay station 1 b are prioritized communications or not. Havingreceived these response messages, the wireless communicationdiscrimination portions 32 a and 32 b of the wireless terminals 3 a and3 b store these response messages.

After this, the call between the wireless terminals 3 a and 3 b begins.The communicated VoIP packets are judged to be prioritized communicationby the priority communication discrimination portions 32 a and 32 b ofthe wireless terminals 3 a and 3 b, and by the priority communicationdiscrimination portions 14 a and 14 b of the wireless relay stations 1 aand 1 b. Thus, the wireless LAN interfaces of the wireless terminals 3a, 3 b and the wireless relay station 1 a are instructed to performprioritized communication.

When the wireless terminal 3 a moves from the region administrated bythe wireless relay station 1 a to the region administrated by thewireless relay station 1 b, the wireless terminal 3 a sends a messagesearching for a wireless relay station 1. The wireless relay station 1b, which is capable of connection, responds to this message. Thewireless terminal 3 a then connects to the wireless relay station 1 b,which has responded (#48).

The stream server communication portion 17 b of the wireless relaystation 1 b requests from the stream server communication portion 17 aof the wireless relay station 1 a the transfer of information relatingto the wireless terminal 3 a (#49). In this situation, the wirelessrelay station 1 a from which this information has been requestedconfirms that guest resources are left over, and if there is no problem,responds to the transfer request (#50). Moreover, since the correlationbetween the wireless terminal 3 and the wireless relay station 1 haschanged, the wireless relay station 1 b notifies the AP manager 5 of thenew correlation (#51).

The wireless relay station 1 a, which has received the Move message,sends the information registered in the entries of the prioritizedcommunication regarding the wireless terminal 3 a to the wireless relaystation 1 b, for the originator of the request (#50). After this, thebandwidth managing portion 11 a of the wireless relay station 1 aeliminates the information registered in the entries of the prioritizedcommunication related to the wireless terminal 3 a from the prioritytable 114 b. On the other hand, the bandwidth managing portion 11 b ofthe wireless relay station 1 b registers the information about theprioritized communication regarding the wireless terminal 3 a in theguest entries of the priority table 114 b. Moreover, the bandwidthmanaging portion 11 b monitors whether a predetermined time T has passedsince the registration, and after the predetermined time T has passed,moves the information registered in the guest entries to the entries forexisting parties.

The wireless relay station 1 b notifies the AP manager 5 that thewireless terminal 3 b is connected (#51). This notification includes theIP address of the wireless terminal 3 b. The AP manager 5 updates theconnection administration table 511 based on this notification.

After this, prioritized communication via the wireless relay station 1 bcontinues.

In order to interrupt the VoIP communication, a Bye message is sent fromone of the wireless terminals. In this example, a Bye message is sentfrom the wireless terminal 3 a. When the IP telephone application 31 asends a Bye message, it is sent via the wireless relay station 1 b tothe SIP server 2 (#52).

The SIP protocol control portion 21 sends the Bye message via thewireless relay station 1 b to the wireless terminal 3 b, which is theother terminal (#53).

The IP telephone application 31 b confirms the Bye message and respondsvia the wireless relay station 1 b, whereupon the SIP protocol controlportion 22 interprets this response (#54).

The SIP protocol control portion 22 notifies the termination of theprioritized communication via the external link portion 23 to the streamserver communication portion 17 b of the wireless relay station 1 b.Receiving this notification, the bandwidth managing portion 11 b of thewireless relay station 1 b eliminates the entry for the correspondingprioritized communication from the priority table 114 b (#55).

The SIP protocol control portion 22 further requests from the AP manager5 the elimination of the information relating to the wireless terminals3 a and 3 b (#56). Receiving this request, the AP manager 5 eliminatesthe entries with information relating to the wireless terminals 3 a and3 b from the connection administration table 511.

The SIP protocol control portion 22 further sends a response message viathe wireless relay station 1 b to the wireless terminal 3 a, and endsall communications relating to the VoIP communication (#57).

With this process, even when the wireless terminal 3 moves and theconnected wireless relay station changes, prioritized communication thatwas performed before the move can be continued after the move. Moreover,resources that have become unnecessary can be assigned by the wirelessrelay stations to other prioritized communications, thus allowingefficient use of the resources for prioritized communication.

Fifth Embodiment

The first to fourth embodiments were explained for the case that a SIPserver is used as the stream server 2. In the fifth embodiment, a userauthentication server is used instead of the stream server 2. The userauthentication server 2 performs user authentication, for example forconnecting wireless terminals 3 to the internet, and stores registeredusers. This is explained with reference to FIG. 14: When there is aconnection request from the wireless terminal 3 a of a registered user(#61), the authentication server 2 requests from the wireless relaystation 1 a registration to the effect that communication by thewireless terminal 3 a is performed as prioritized communication,regardless of the application type (#62, #63), whereas with regard tothe connection request from the wireless terminal 3 b of an unregistereduser, the authentication server 2 may notify the wireless relay station1 that prioritized communication is not necessary, regardless of theapplication type (#66 to #68). Thus, communication between the wirelessterminal 3 a and the wireless relay station 1, for example, isprioritized regardless of the application type, such as VoIPcommunication or HTTP communication (#64, #65). Conversely,communication between the wireless terminal 3 b and the wireless relaystation 1 is handled as non-prioritized communication regardless of theapplication type (#69, #70). Alternatively, the authentication server 2may request the wireless relay station 1 to handle all communication,such as VoIP communication or HTTP communication, regarding connectionrequests from registered users as prioritized communication, and tohandle only HTTP communication regarding connection requests ofunregistered users as prioritized communication.

Other Embodiments

(A) In the above-described first to fourth embodiments, in response to aquery about the availability of resources for prioritized communicationfrom the SIP server 2, the wireless relay station 1 sends back a replyindicating whether resources are available. However, by changing thedata type, it is sometimes possible to perform prioritized communicationwith little resources. For example, in VoIP communication, it ispossible to change, for example, the type of the audio data that arecommunicated, depending on the capability of the communicating wirelessterminals or the available bandwidth or the like. More specifically, inVoIP calls, audio data of the G.711 standard in which the transfer speedof the audio data is 64 kbps are often used. On the other hand, thereare several standards such as the G.722 standard (8 kbps), in whichaudio compression is performed. Accordingly, the wireless relay stationmay respond: “The bandwidth for G.711 cannot be secured, but theresources for G.722 are available.”

Moreover, if there is a request from the wireless terminal 3 to connectby video and audio, then the wireless relay station 1 may respond thatthe resources are available for a connection by audio only. Under theSIP, also information what is used as the media is specified in thesignal. Using this information, it is possible to realize prioritizedcommunication within a scope that can be afforded by the resources forprioritized communication by changing the media connected to the SIPserver 2 in accordance with the response from the wireless relay station1 and notifying the other party.

FIG. 15 shows an example of the process flow for this case. After thewireless terminals 3 a and 3 b have wirelessly connected to the wirelessrelay station 1 (#81, #84) and registered (#82, #83, #85, #86), thewireless terminal 3 a requests the communication of audio and video fromthe wireless relay station 1 (#87). The SIP server 2 sends a bandwidthconfirmation message to the wireless relay station 1 regarding thebandwidth for audio and video communication (#88). Assuming thatprioritized communication is possible in the case of audio communicationonly, the wireless relay station 1 sends back its OK for audiocommunication (#89). This is also notified to the wireless terminal 3 b(#90). At the same time, the wireless relay station 1 returns a Tryingmessage to the wireless terminal 3 a (#91). After this, the wirelessterminal 3 b sends a Ringing message via the SIP server 2 to thewireless terminal 3 a (#92, #93). The SIP server 2 waits for the OK fromthe wireless terminal 3 b, and registers in the wireless relay station 1the prioritized communication for audio (#95). After the fact that theaudio communication is prioritized communication has been notified tothe wireless terminal 3 a (#96), the wireless terminal 3 a sends back anACK message via the SIP server 2 to the wireless terminal 3 b (#97,#98), and the communication begins. The communication is terminated in asimilar manner as explained above (#99 to #103).

(B) The scope of the present invention also includes programs executingthe above-described methods and computer-readable recording mediastoring such programs. Examples of such recording media includecomputer-readable flexible disks, hard disks, semiconductor memories,CD-ROMs, DVDs, and magneto-optical disks (MOs) among others.

The invention may be embodied in other forms without departing from thespirit or essential characteristics thereof. The embodiments disclosedin this application are to be considered in all respects as illustrativeand not limiting. The scope of the invention is indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are intended to be embraced therein.

1. A communication relay method executed by a wireless communicationsystem comprising a plurality of wireless terminals, a relay deviceconnected by a wireless network to the wireless terminals, and acommunication managing device connected to the relay device by a wirednetwork, the method comprising steps of storing, in the relay device, apriority table in which identifiers of communications relayed withhigher priority are registered; relaying, by the relay device,communication specified by the communication identifiers stored in thepriority table with higher priority than other communication; receiving,by the communication managing device, communication start requests fromany of the wireless terminals and sending communication identifiersspecifying the communications that are about to be started to the relaydevice; receiving, by the relay device, the communication identifiersand registering the received communication identifiers in the prioritytable, to an extent that a proportion S/U of a sum S of consumptionbandwidths of the communications specified by the communicationidentifiers registered in the priority table to the available bandwidthU of the wireless network does not exceed a predetermined upper limit.2. The communication relay method according to claim 1, wherein therelay device registers communication identifiers in the priority tableto an extent that the number of communications specified by thecommunication identifiers registered in the priority table is notgreater than a predetermined number of connections.
 3. The communicationrelay method according to claim 1, wherein the relay device registerscommunication identifiers in the priority table to an extent that thesum of the consumption bandwidths of the communications specified by thecommunication identifiers registered in the priority table is notgreater than an available bandwidth of the wireless network.
 4. Thecommunication relay method according to claim 1, wherein the relaydevice reserves, in the priority table, entries for guests in order totake over a relay of prioritized communication data that has beenrelayed by another relay device.
 5. The communication relay methodaccording to claim 4, wherein the relay device exchanges with anotherrelay device communication identifiers specifying communication datarelayed with higher priority, and updates the priority table based on aresult of this exchange.
 6. A communication relay system comprising: arelay device connected by a wireless network to a plurality of wirelessterminals; and a communication managing device connected by a wirednetwork to the relay device; wherein the relay device comprises: apriority table storing, from among a plurality of communications bywireless terminals, identifiers of those communications that are relayedwith higher priority; a relay means for relaying communication specifiedby the communication identifiers stored in the priority table withhigher priority than other communication; and a table managing means forreceiving communication identifiers from the communication managingdevice, and registering received communication identifiers in thepriority table, to an extent that a proportion S/U of a sum S ofconsumption bandwidths of the communications specified by thecommunication identifiers registered in the priority table to theavailable bandwidth U of the wireless network does not exceed apredetermined upper limit; wherein the communication managing devicereceives communication start requests from any of the wireless terminalsand sends to the relay device communication identifiers specifying thecommunication that are about to be started.
 7. A communication managingdevice connected by a wired network to a relay device that is connectedby a wireless network to a plurality of wireless terminals, thecommunication managing device comprising: a requesting means forreceiving communication start requests from any of the wirelessterminals and sending to the relay device an identifier of thecommunications that are about to be started and requests for prioritizedrelay of these communications; a receiving means for receiving from therelay device responses to these requests; and a notification means forsending notifications to the wireless terminals depending on the contentof the response.
 8. A relay device connected by a wireless network to aplurality of wireless terminals, the relay device comprising: aconnection means for connecting via a wired network to a communicationmanaging device managing communication of the wireless terminals; astorage means for storing a priority table in which identifiers ofcommunications relayed with higher priority are registered; a priorityrelay means for relaying communication data specified by thecommunication identifiers stored in the priority table with higherpriority than other communication; a request receiving means forreceiving from the communication managing device requests to register acommunication identifier in the priority table; and a priority tableupdating means for registering the received communication identifiers inthe priority table, to an extent that a proportion S/U of a sum S ofconsumption bandwidths of the communications specified by thecommunication identifiers registered in the priority table to theavailable bandwidth U of the wireless network does not exceed apredetermined upper limit.